US20170229275A1 - Particle charger - Google Patents
Particle charger Download PDFInfo
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- US20170229275A1 US20170229275A1 US15/501,935 US201415501935A US2017229275A1 US 20170229275 A1 US20170229275 A1 US 20170229275A1 US 201415501935 A US201415501935 A US 201415501935A US 2017229275 A1 US2017229275 A1 US 2017229275A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J27/00—Ion beam tubes
- H01J27/02—Ion sources; Ion guns
- H01J27/022—Details
- H01J27/024—Extraction optics, e.g. grids
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
- B03C3/017—Combinations of electrostatic separation with other processes, not otherwise provided for
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
- B03C3/34—Constructional details or accessories or operation thereof
- B03C3/38—Particle charging or ionising stations, e.g. using electric discharge, radioactive radiation or flames
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
- B03C3/34—Constructional details or accessories or operation thereof
- B03C3/40—Electrode constructions
- B03C3/41—Ionising-electrodes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
- B03C3/34—Constructional details or accessories or operation thereof
- B03C3/40—Electrode constructions
- B03C3/45—Collecting-electrodes
- B03C3/47—Collecting-electrodes flat, e.g. plates, discs, gratings
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
- B03C3/34—Constructional details or accessories or operation thereof
- B03C3/40—Electrode constructions
- B03C3/45—Collecting-electrodes
- B03C3/49—Collecting-electrodes tubular
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/02—Investigating particle size or size distribution
- G01N15/0266—Investigating particle size or size distribution with electrical classification
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
- G01N27/622—Ion mobility spectrometry
- G01N27/623—Ion mobility spectrometry combined with mass spectrometry
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J27/00—Ion beam tubes
- H01J27/02—Ion sources; Ion guns
- H01J27/20—Ion sources; Ion guns using particle beam bombardment, e.g. ionisers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
- H01J37/32082—Radio frequency generated discharge
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
- H01J37/32082—Radio frequency generated discharge
- H01J37/321—Radio frequency generated discharge the radio frequency energy being inductively coupled to the plasma
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
- H01J37/32357—Generation remote from the workpiece, e.g. down-stream
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/32431—Constructional details of the reactor
- H01J37/3244—Gas supply means
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/32431—Constructional details of the reactor
- H01J37/32532—Electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/02—Details
- H01J49/06—Electron- or ion-optical arrangements
- H01J49/061—Ion deflecting means, e.g. ion gates
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/02—Details
- H01J49/10—Ion sources; Ion guns
- H01J49/12—Ion sources; Ion guns using an arc discharge, e.g. of the duoplasmatron type
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/02—Details
- H01J49/10—Ion sources; Ion guns
- H01J49/14—Ion sources; Ion guns using particle bombardment, e.g. ionisation chambers
- H01J49/145—Ion sources; Ion guns using particle bombardment, e.g. ionisation chambers using chemical ionisation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C2201/00—Details of magnetic or electrostatic separation
- B03C2201/06—Ionising electrode being a needle
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N2015/0038—Investigating nanoparticles
Definitions
- the present invention relates to a particle charger for electrically charging microparticles in a gas.
- Aerosols Micro-sized liquid or solid particles suspended in a gas are generally called aerosols. Most of the contaminants contained in the exhaust gas of automobiles or in the smoke emitted from manufacturing plants are aerosols. In particular, aerosols with a particle diameter smaller than 1 ⁇ m, or so-called “nano-aerosols”, have raised concerns about their unfavorable influences on health. Therefore, measuring their particle diameters or distribution of particle diameters has been extremely important in such areas as environmental measurement and assessment.
- DMA differential mobility analyzer
- a comparatively traditional type of particle charger is one which uses alpha rays emitted from americium (Am), beta rays emitted from krypton (Kr) or similar radiations as the ion source and forces the ions generated by this ion source to come in contact with the particles as the charging target to electrically charge those particles (see Non Patent Literature 1).
- This device is also called the “bipolar diffusion neutralizer”, or simply “neutralizer”.
- this type of particle charger has problems associated with the use of the radiation source, such as the necessity of being operated with the greatest concern for safety as well poor portability. Accordingly, in recent years, as a substitute for this particle charger, a particle charger using an ion source which employs electric discharge, such as corona discharge, has been increasingly used. For example, as described in Patent Literature 2, this type of particle charger ionizes an appropriate kind of carrier-gas molecules by corona discharge or similar electric discharge and forces the generated ions to come in contact with sample particles as the charging target to electrically charge those particles.
- FIG. 8 shows one example of the configuration of a particle classifying and observing system including the previously described type of particle charger along with a particle classifier.
- the particles as the measurement target collected with a sampler 100 are sent into the particle charger 200 , which electrically charges those panicles and sends them to the particle classifier 300 .
- the charged particles sent to the particle classifier 300 are classified according to the difference in their electrical mobilities. After that, those particles are sent to a particle counter 400 so as to be counted per particle diameter, or are collected with a collector 500 so as to be observed through an observing device 600 .
- Patent Literature 1 JP 4905040 B
- Patent Literature 1 JP 2007-305498 A
- Non Patent Literature 1 Sato, Sakurai and Ehara, “The Relation between the Charged Fractions of the Aerosol Charge Neutralizer and the Time Change of the Ion Mobility”, J. Inst. Electrostat. Jpn., Vol. 35, No.1, 2011, pp. 14-19
- the present invention has been developed in view of the aforementioned point. Its objective is to provide a particle charger which can suppress the occurrence frequency of the multi-charging and thereby equalize the valence of the charged particles.
- the particle charger according to the present invention includes:
- a filter composed of a plurality of electrodes extending in a virtual surface partitioning the inside of the housing into a first space and a second space;
- a potential gradient creator for creating a potential gradient within the housing so as to make the gas ion and a charged particle resulting from a contact of the aforementioned particle with the gas ion move from the first space toward the second space;
- an AC voltage supplier for applying an AC voltage to each of the electrodes forming the filter, where the voltages applied to any two electrodes neighboring each other among the plurality of electrodes have a phase difference;
- a controller for controlling the AC voltage supplier so as to apply, to the plurality of electrodes, voltages which are previously determined so that, among the charged particle and the gas ion moving from the first space toward the second space, the charged particle is allowed to pass through a gap between the electrodes while the gas ion is trapped by one of the electrodes;
- a charged particle extractor for extracting the charged particle admitted to the second space to the outside of the housing.
- the charged particle generated by coming in contact with the gas ion in the first space moves from the first space toward the second space due to the effect of the potential gradient and eventually reaches the second space through the filter.
- the gas ion is also urged to move from the first space toward the second space, the gas ion is trapped by the filter and cannot reach the second space.
- the charged particle generated within the first space can be promptly transferred into the space where no gas ion is present, i.e. the second space.
- the contact time between the gas ion and the particle to be charged is reduced, so that the occurrence of the multi-charging is suppressed.
- the relationship between the diameter of the particle to be charged and the suitable voltages to be applied to the filter for trapping the gas ion while allowing the passage of the charged particle is experimentally investigated and stored beforehand.
- the controller determines the application voltages corresponding to that target diameter with reference to the stored information, and controls the AC voltage supplier so that the determined voltages skill be applied to the electrodes forming the filter.
- the “virtual surface” in the present invention may be a flat surface or curved surface.
- the gas supplier may introduce, into the first space, gas ions produced at a different location, or it may generate gas ions within the first space.
- the AC voltage supplier may apply a sinusoidal voltage or non-sinusoidal voltage (e.g. rectangular voltage) to each electrode as the AC voltage. Applying a rectangular voltage has the advantage of facilitating the frequency change, duty-cycle control, phase control and other operations on the AC voltage, since rectangular voltages can be generated by turning a DC voltage on and off using a semiconductor switching element.
- the shape of the filter is not specifically limited.
- it may be composed of a plurality of rod electrodes arranged parallel to each other, or a plurality of rod electrodes arranged in the form of a grid.
- a concentric arrangement of a plurality of circular electrodes is also possible.
- the charged particle extractor can be configured, for example, so as to produce a stream of gas in a direction intersecting with the direction from the first space toward the second space, and extract the charged particle from the housing to the outside by this stream of gas.
- the charged particle extractor can also be configured so as to create a potential gradient in a direction intersecting with the direction from the first space toward the second space, and extract the charged particle from the housing to the outside by using the motion of the charged particle along the potential gradient.
- the particle charger according to the present invention can suppress the multi-charging and increase the ratio of the singly-charged particles.
- FIG. 1A is a model diagram showing a vertical section of a particle charger according to one embodiment of the present invention
- FIG. 1B is a section viewed along the arrows A-A in FIG. 1A .
- FIG. 2 is a diagram illustrating the principle of separating charged particles from gas ions by a filter.
- FIG. 3A is a model diagram showing a vertical section of a particle charger according to another embodiment of the present invention
- FIG. 3B is a section viewed along the arrows A-A in FIG. 3A .
- FIG. 4 is a plan view showing an example of the filter in a grid-like form.
- FIG. 5 is a plan view showing an example of the filter in a concentric form.
- FIG. 6 is a plan view showing an example of the filter in a double spiral form.
- FIG. 7 is a diagram showing a configuration in which the extraction of the charged particles in the present invention is achieved by using a potential difference.
- FIG. 8 is a block diagram showing one example of the particle classifying and observing system.
- FIG. 9 is a diagram showing the result of a simulation of the trajectory of the gas ion in the present invention.
- FIG. 10 is a diagram showing the result of a simulation of the trajectory of the charged particle in the present invention.
- FIGS. 1A and 1B are schematic configuration diagrams of a particle charger according to the present embodiment, where FIG. 1A shows a vertical section of the particle charger, and FIG. 1B shows a section viewed along the arrows A-A in FIG. 1A .
- FIG. 2 is a perspective view of the filter in the same particle charger. It should be noted that the front-rear, up-down, and right-left directions mentioned in the following descriptions are defined so that the X, Y and Z directions in FIG. 1A correspond to the leftward, frontward and upward directions, respectively.
- the particle charger according to the present embodiment which is designed to be placed between the sampler 100 and the classifier 300 in a particle classifying and observing system as shown in FIG. 8 , includes a particle-charging unit 20 and a gas-ion generating unit 10 (which corresponds to the gas ion supplier in the present invention) located above the former unit.
- the particle-charging unit 20 has a substantially rectangular parallelepiped chamber 21 (which corresponds to the housing in the present invention).
- a first upward-side opening 22 (which corresponds to the particle introducer in the present invention) and a second upward-side opening 23 are vertically arranged, both of which are the openings for allowing an inflow of gas from the outside into the chamber 21 .
- a first downward-side opening 24 and a second downward-side opening 25 are vertically arranged, both of which are the openings for discharging gas from the chamber 21 to the outside.
- This chamber 21 contains a first plate electrode 26 arranged along the top face of the chamber 21 , a second plate electrode 27 arranged along the bottom face of the chamber 21 , and a filter 28 located between the first and second plate electrodes 26 and 27 .
- This filter 28 is composed of a plurality of rod electrodes 28 a and 28 b arranged parallel to each other and at regular intervals in a plane parallel to the first and second plate electrodes 26 and 27 , with each rod electrode extending in the front-rear direction.
- the filter 28 is composed of a large number of electrodes 28 a and 28 b , as shown in FIG. 2 . However, for simplicity, only six electrodes 28 a and 28 b are shown in FIGS. 1A and 1B .
- the space between the first plate electrode 26 and the filter 28 is called the “first space 29 ”
- the space between the filter 28 and the second plate electrode 27 is called the “second space 30 ”.
- a DC power source 31 for applying voltage V 1 to the first plate electrode 26 and voltage V 2 to the second plate electrode 27 , as well as a first AC power source 32 and a second AC power source 33 for applying AC voltages to the electrodes forming the filter 28 .
- the first and second AC power sources 32 and 33 correspond to the AC voltage supplier in the present invention.
- the first plate electrode 26 , second plate electrode 27 and DC power source 31 cooperating with each other function as the potential gradient creator in the present invention.
- the first AC power source 32 supplies AC voltage V 3 sin( ⁇ t) to the electrodes 28 a located at the odd-numbered positions as counted from the left end among the large number of electrodes 28 a and 28 b forming the filter 28 .
- the second AC power source 33 supplies AC voltage V 4 sin( ⁇ t+ ⁇ ), which has a phase difference of ⁇ from the AC voltage supplied by the first AC power source 32 , to the electrodes 28 b located at the even-numbered positions as counted from the left end among the large number of electrodes.
- phase difference ⁇ There is no specific limitation on the phase difference ⁇ , although a value within a range of 90° to 270° is preferable.
- the amplitudes V 3 and V 4 , frequency ⁇ , as well as phase difference ⁇ of the AC voltages supplied by the first and second AC power sources 32 and 33 are controlled by a controller 35 .
- the controller 35 also operates the aforementioned DC power source 31 and a discharge power source 14 (which will be described later), although the control lines for these devices are omitted from the figure for simplicity.
- the gas-ion generating unit 10 also has a substantially rectangular parallelepiped chamber 11 , which contains a needle-shaped discharge electrode 12 vertically extending downward from the top face. Located on the inner bottom of the same chamber 11 is a plate-shaped ground electrode 13 which forms a pair with the discharge electrode 12 . Outside the chamber 11 , a discharge power source 14 for applying a voltage for inducing electric discharge to the discharge electrode 12 is provided.
- a gas introduction port 15 for introducing a gas for gas-ion generation (“ionization gas”) into the chamber 11 is formed on the side wall of the chamber 11 , while an opening for allowing an outflow of the ions generated within the chamber 11 (those ions are hereinafter called the “gas ions”) into the first space 29 is formed in the bottom wall of the chamber 11
- the ground electrode 13 , top wall of the chamber 21 of the particle-charging unit 20 , and first plate electrode 26 are also provided with through-holes formed at the position corresponding to the aforementioned opening. The opening and those through-holes form a gas-ion discharge port 16 through which the inner space of the chamber 21 of the particle-charging unit 20 communicates with that of the chamber 11 of the gas-ion generating unit 10 .
- an ionization gas e.g. air
- a voltage is applied from the discharge power source 14 to the discharge electrode 12 .
- electric discharge occurs in the space between the discharge electrode 12 and the ground electrode 13 , whereby the ionization gas within the chamber 11 is ionized.
- the polarity of the thereby generated gas ions depends on the polarity of the voltage applied to the discharge electrode 12 . In the following description, it is assumed that the gas ions are positive ions.
- the gas ions generated in the gas-ion generating unit 10 flow through the gas-ion discharging port 16 into the first space 29 in the particle-charging unit 20 .
- the particles collected as the charging target by the sampler 100 ( FIG. 8 ) in the previous stage and carried by a carrier gas are introduced from the first upward-side opening 22 into the first space 29 .
- a carrier gas supplied from a carrier gas supplier 34 (which does not contain the aforementioned particles) is introduced through the second upward-side opening 23 into the second space 30 .
- a stream of carrier gas, directed from left to right, is formed within each of the first and second spaces 29 and 30 of the chamber 11 (as indicated by the thick black arrows in FIG. 1A ).
- the carrier gas supplier 34 , second upward-side opening 23 and second downward-side opening 25 correspond to the charged particle extractor in the present invention.
- the particles to be charged introduced from the first upward-side opening 22 into the first space 29 come in contact with the gas ions and become positively charged by receiving electric charges from the gas ions.
- the potential V 1 of the first plate electrode 26 is higher than the potential V 2 of the second plate electrode 27 , i.e. V 1 >V 2 , whereby a potential gradient whose level decreases in the direction indicated by the thick white arrows in FIG. 1A is formed between the two electrodes. Since both the gas ions introduced into the first space 29 and the particles electrically charged within the first space 29 (which are hereinafter called the “charged particles”) are positively charged, they follow the potential gradient and move downward (i.e. toward the second space 30 ) within the chamber 21 .
- the filter 28 provided between the first and second spaces 29 and 30 is supplied with the AC voltages whose phases differ from each other between any two electrodes 28 a and 28 b neighboring each other in the right-left direction. Therefore, the gas ions and charged particles which attempt to pass through the gap between the two electrodes 28 a and 28 b while moving downward within the chamber 21 in the previously described manner alternately experience attractive and repulsive forces from the electrodes 28 a and 28 b on both sides. In this process, an object having a comparatively high mobility (which is a value representing how easily a charged particle can move in an electric field) is quickly attracted to and collides with one of the electrodes, failing to pass through the gap between the two electrodes.
- a comparatively high mobility which is a value representing how easily a charged particle can move in an electric field
- an object having a comparatively low mobility is attracted toward the opposite direction due to the attractive force from the other electrode before it collides with one of the electrodes. Therefore, this object can pass through the gap between the two electrodes 28 a and 28 b, oscillating in the right-left direction in a stable manner.
- the charged panicles generated by the panicle charger in the present embodiment have sufficiently lower mobilities than the gas ions. Accordingly, by appropriately adjusting the values related to the conditions (amplitude, frequency and phase difference) of the voltages applied by the first and second AC power sources 32 and 33 , it is possible to realize the situation that only the charged particles are allowed to pass through the filter 28 and reach the second space 30 while the gas ions are trapped by the filter 28 and prevented from reaching the second space 30 .
- the charged particles 42 whose mobility is relatively low oscillate in a stable manner and pass through the gaps between the neighboring electrodes 28 a and 28 b, to successfully reach the second space 30 .
- the gas ions 41 whose mobility is relatively high, are attracted to and collide with the electrode 28 a or 28 b when they come to a certain distance to the filter 28 , failing to reach the second space 30 .
- the conditions of the voltages applied to the filter 28 so as to allow the passage of only the charged particles in the previously described manner are, for example, previously investigated by experiments for each condition (kind, diameter, etc.) of the particles as the charging target and stored in a storage unit 36 .
- the controller 35 refers to the information stored in the storage unit 36 , determines the conditions of the voltages corresponding to the target particle, and controls the first and second AC power sources 32 and 33 so that those voltages are applied to the electrodes 28 a and 28 b forming the filter 28 .
- the charged particles which have reached the second space 30 are carried rightwards within the second space 30 by the stream of ca gas directed from the second upward-side opening 23 to the second downward-side opening 25 . Subsequently, the charged particles are extracted from the second downward-side opening 25 to the outside of the chamber 11 and sent to the particle classifier 300 provided in the subsequent stage ( FIG. 8 ). It should be noted that the amount of voltage applied from the DC power source 31 , flow rate of the carrier gas supplied from the carrier gas supplier 34 and other relevant parameters are previously adjusted by the controller 35 so that the charged particles which have passed through the filter 28 and reached the second space 30 will be sent to the outside of the chamber 11 without colliding with the second plate electrode 27 .
- the charged particles generated by coming in contact with the gas ions are promptly extracted to the area where no gas ion is present (the second space 30 ), whereby the occurrence of the multi-charging is effectively suppressed and the ratio of singly-charged particles is increased. Therefore, in the process of extracting particles having a certain diameter by classification, the mixture of unwanted particles which have different diameters and yet have approximately the same mobility due to the multi-charging is suppressed. Therefore, for example, the accuracy of the particle diameter distribution can be improved, or a high level of collection efficiency can be achieved for particles having a specific particle diameter.
- the previously described example is concerned with the configuration in which the gas ions are positive ions and the particles are positively charged by corning into contact with those gas ions. It is also possible to use the opposite configuration in which the gas ions are negative ions and the particles are negatively charged by coming into contact with the gas ions. In this case, the potential V 1 of the first plate electrode 26 is set to be lower than the potential V 2 of the second plate electrode 27 .
- the electrodes 28 a and 28 b forming the filter 28 are arranged so that they extend in the right-left direction, i.e. in the orthogonal direction to the stream of the carrier gas.
- the arrangement is not limited to this form.
- the plurality of electrodes 51 a and 51 b forming the filter 51 may be arranged so that they extend in the front-rear direction, i.e. in the parallel direction to the stream of the carrier gas.
- the filter may be configured as shown in FIG. 4 in which the filter 52 is composed a plurality of electrodes 52 a and 52 b arranged in a grid-like form.
- the electrode group consisting of the vertically arrayed electrodes 52 a and 52 b and the one consisting of the horizontally arrayed electrodes 52 a and 52 b should be separated from each other in the direction of the electric field created by the first and second plate electrodes 26 and 27 (in the up-down direction in FIG. 1A ). It is also possible to use a configuration as shown in FIG.
- the filter 53 is composed of a plurality of circular electrodes 53 a and 53 b arranged in a concentric form, or as shown in FIG. 6 , in which the filter 54 is composed of a plurality of spiral electrodes 54 a and 54 b.
- two AC voltages having a phase difference between any two electrodes 52 a and 52 b, 53 a and 53 b, or 54 a and 54 b neighboring each other are applied in the previously described manner.
- each electrode is also not specifically limited. Other than the circular shape as shown in FIGS. 1A and 1B as well as and FIGS. 3A and 3B , it may have a polygonal shape, such as a triangle or quadrangle.
- the charged particles which have reached the second space 30 are extracted to the outside of the chamber 21 by a stream of carrier gas.
- the extraction of the charged particles may be achieved by an extracting electric field created within the second space 30 .
- an extraction electrode 62 and opposite electrode 61 are arranged on the side wall of the chamber 21 of the particle charger 20 , facing each other across the second space 30 , with a DC voltage applied between the two electrodes to create an extracting electric field having a potential gradient whose level decreases in the direction from the opposite electrode 61 toward the extraction electrode 62 (as indicated by the thick halftone arrows in FIG. 7 ).
- the (positively) charged particles which have passed through the filter 28 and reached the second space 30 in the previously described manner move in the direction from the opposite electrode 61 to the extraction electrode 62 and are eventually extracted from the opening 63 formed in the extraction electrode 62 to the outside of the chamber 11 .
- a mesh-like electrode may be used as the extraction electrode, with the charged particles extracted through the openings of the mesh.
- an extracting electric field having the opposite potential gradient whose level increases from the opposite electrode 61 toward the extraction electrode is created.
- the particle extractor in the present invention may also be configured to extract the charged particles by using both the stream of carrier gas and the extracting electric field.
- the opposite electrode 61 in FIG. 7 is also be provided with an opening so as to introduce the carrier gas from this opening and thereby create a stream of carrier gas directed from the same opening toward the opening 63 of the extraction electrode.
- the particle charger according to the present invention can be applied not only in a particle classifying and observing system as shown in FIG. 8 ; for example, it can also be used as an ionizing unit in a mass spectrometer.
- FIGS. 1A and 1B a system as shown in FIGS. 1A and 1B was simulated under the following conditions:
- the voltage V 1 applied to the first place electrode 26 was 1050 V.
- the voltage V 2 applied to the second place electrode 27 was ⁇ 1050 V.
- the electrodes 28 a and 28 b were 1.0 mm in diameter and arranged at intervals of 1.5 mm.
- the gas ions had a mass of 32 Da and a mobility of 1.0E ⁇ 04 m 2 /VS, while the charged particles had a mass of 1.0E+08 Da and a mobility of 2.7E ⁇ 08 m 2 /VS.
Abstract
A particle charger is provided with: a filter (28) partitioning the inside of a housing (20) into a first space (29) and second space (30); a particle introducer (22) for introducing a particle into the first space; a gas ion supplier (10) for supplying the first space with a gas ion; a potential gradient creator (26, 27, 31) for creating a potential difference within the housing so as to make the gas ion and a charged particle resulting from a contact of the aforementioned particle with the gas ion move toward the second space; an AC voltage supplier (32, 33) for applying AC voltages having a phase difference to the neighboring electrodes (28 a, b) included in the filter; a controller (35) for performing a control for applying, to the plurality of electrodes, predetermined voltages so as to allow the charged particle to pass through a gap between the electrodes while trapping the gas ion by the electrodes; and a charged particle extractor (23, 25, 34) for extracting the charged particle admitted to the second space to the outside of the housing. By this configuration, the occurrence frequency of the multi-charging is suppressed.
Description
- The present invention relates to a particle charger for electrically charging microparticles in a gas.
- Micro-sized liquid or solid particles suspended in a gas are generally called aerosols. Most of the contaminants contained in the exhaust gas of automobiles or in the smoke emitted from manufacturing plants are aerosols. In particular, aerosols with a particle diameter smaller than 1 μm, or so-called “nano-aerosols”, have raised concerns about their unfavorable influences on health. Therefore, measuring their particle diameters or distribution of particle diameters has been extremely important in such areas as environmental measurement and assessment. As a device for measuring the particle-diameter distribution of aerosols (particle classifier), a differential mobility analyzer (DMA), which classifies microparticles using the difference in the moving speed of charged microparticles within an electric field (electric mobility), has been popularly used (see Patent Literature 1 or other documents).
- In a measurement using a DMA, the particles to be subjected to the measurement (aerosols) need to be electrically charged in advance of the measurement. To this end, several types of particle chargers have been conventionally used. A comparatively traditional type of particle charger is one which uses alpha rays emitted from americium (Am), beta rays emitted from krypton (Kr) or similar radiations as the ion source and forces the ions generated by this ion source to come in contact with the particles as the charging target to electrically charge those particles (see Non Patent Literature 1). This device is also called the “bipolar diffusion neutralizer”, or simply “neutralizer”.
- However, this type of particle charger has problems associated with the use of the radiation source, such as the necessity of being operated with the greatest concern for safety as well poor portability. Accordingly, in recent years, as a substitute for this particle charger, a particle charger using an ion source which employs electric discharge, such as corona discharge, has been increasingly used. For example, as described in Patent Literature 2, this type of particle charger ionizes an appropriate kind of carrier-gas molecules by corona discharge or similar electric discharge and forces the generated ions to come in contact with sample particles as the charging target to electrically charge those particles.
-
FIG. 8 shows one example of the configuration of a particle classifying and observing system including the previously described type of particle charger along with a particle classifier. In this particle classifying and observing system, the particles (aerosols) as the measurement target collected with asampler 100 are sent into theparticle charger 200, which electrically charges those panicles and sends them to theparticle classifier 300. The charged particles sent to theparticle classifier 300 are classified according to the difference in their electrical mobilities. After that, those particles are sent to aparticle counter 400 so as to be counted per particle diameter, or are collected with acollector 500 so as to be observed through anobserving device 600. - Patent Literature 1: JP 4905040 B
- Patent Literature 1: JP 2007-305498 A
- Non Patent Literature 1: Sato, Sakurai and Ehara, “The Relation between the Charged Fractions of the Aerosol Charge Neutralizer and the Time Change of the Ion Mobility”, J. Inst. Electrostat. Jpn., Vol. 35, No.1, 2011, pp. 14-19
- In the previously described particle charger, it is necessary to equalize the number of charges (valence) of the sample particles in order to improve the classifying accuracy in the particle classifier located in the subsequent stage. However, in general, large-sized particles (heavy particles) are likely to vary in their valence due to the frequent occurrence of multi-charging.
- The present invention has been developed in view of the aforementioned point. Its objective is to provide a particle charger which can suppress the occurrence frequency of the multi-charging and thereby equalize the valence of the charged particles.
- A commonly known reason for the easy occurrence of the multi-charging on the large-sized particles is that large-sized particles have larger surface areas and therefore higher chances of contact with the ions than small-sized particles. Additionally, there is another possible reason: Larger particles move slowly in a gas stream, so that they reside within the particle charger for a longer period of time and have higher chances of contact with the ions than smaller particles. Accordingly, the present inventors have carried out intensive research so as to reduce the residence time of the sample particles in the area where the gas ions are present within the particle charger. Consequently, the present invention has been created.
- That is to say, the particle charger according to the present invention includes:
- a) a housing;
- b) a filter composed of a plurality of electrodes extending in a virtual surface partitioning the inside of the housing into a first space and a second space;
- c) a particle introducer for introducing a particle to be charged into the first space;
- d) a gas ion supplier for supplying the first space with a gas ion;
- e) a potential gradient creator for creating a potential gradient within the housing so as to make the gas ion and a charged particle resulting from a contact of the aforementioned particle with the gas ion move from the first space toward the second space;
- f) an AC voltage supplier for applying an AC voltage to each of the electrodes forming the filter, where the voltages applied to any two electrodes neighboring each other among the plurality of electrodes have a phase difference;
- g) a controller for controlling the AC voltage supplier so as to apply, to the plurality of electrodes, voltages which are previously determined so that, among the charged particle and the gas ion moving from the first space toward the second space, the charged particle is allowed to pass through a gap between the electrodes while the gas ion is trapped by one of the electrodes;
- h) a charged particle extractor for extracting the charged particle admitted to the second space to the outside of the housing.
- By this configuration, the charged particle generated by coming in contact with the gas ion in the first space moves from the first space toward the second space due to the effect of the potential gradient and eventually reaches the second space through the filter. Although the gas ion is also urged to move from the first space toward the second space, the gas ion is trapped by the filter and cannot reach the second space. In this manner, the charged particle generated within the first space can be promptly transferred into the space where no gas ion is present, i.e. the second space. As a result, the contact time between the gas ion and the particle to be charged is reduced, so that the occurrence of the multi-charging is suppressed.
- Specifically, for example, in the particle charger according to the present invention, the relationship between the diameter of the particle to be charged and the suitable voltages to be applied to the filter for trapping the gas ion while allowing the passage of the charged particle (e.g. amplitude, frequency, phase difference between the neighboring electrodes, etc.) is experimentally investigated and stored beforehand. When the target diameter of the particle to be charged is specified, the controller determines the application voltages corresponding to that target diameter with reference to the stored information, and controls the AC voltage supplier so that the determined voltages skill be applied to the electrodes forming the filter.
- The “virtual surface” in the present invention may be a flat surface or curved surface. The gas supplier may introduce, into the first space, gas ions produced at a different location, or it may generate gas ions within the first space. The AC voltage supplier may apply a sinusoidal voltage or non-sinusoidal voltage (e.g. rectangular voltage) to each electrode as the AC voltage. Applying a rectangular voltage has the advantage of facilitating the frequency change, duty-cycle control, phase control and other operations on the AC voltage, since rectangular voltages can be generated by turning a DC voltage on and off using a semiconductor switching element.
- The shape of the filter is not specifically limited. For example, it may be composed of a plurality of rod electrodes arranged parallel to each other, or a plurality of rod electrodes arranged in the form of a grid. A concentric arrangement of a plurality of circular electrodes is also possible.
- The charged particle extractor can be configured, for example, so as to produce a stream of gas in a direction intersecting with the direction from the first space toward the second space, and extract the charged particle from the housing to the outside by this stream of gas.
- The charged particle extractor can also be configured so as to create a potential gradient in a direction intersecting with the direction from the first space toward the second space, and extract the charged particle from the housing to the outside by using the motion of the charged particle along the potential gradient.
- As described to this point, the particle charger according to the present invention can suppress the multi-charging and increase the ratio of the singly-charged particles.
-
FIG. 1A is a model diagram showing a vertical section of a particle charger according to one embodiment of the present invention, andFIG. 1B is a section viewed along the arrows A-A inFIG. 1A . -
FIG. 2 is a diagram illustrating the principle of separating charged particles from gas ions by a filter. -
FIG. 3A is a model diagram showing a vertical section of a particle charger according to another embodiment of the present invention, andFIG. 3B is a section viewed along the arrows A-A inFIG. 3A . -
FIG. 4 is a plan view showing an example of the filter in a grid-like form. -
FIG. 5 is a plan view showing an example of the filter in a concentric form. -
FIG. 6 is a plan view showing an example of the filter in a double spiral form. -
FIG. 7 is a diagram showing a configuration in which the extraction of the charged particles in the present invention is achieved by using a potential difference. -
FIG. 8 is a block diagram showing one example of the particle classifying and observing system. -
FIG. 9 is a diagram showing the result of a simulation of the trajectory of the gas ion in the present invention. -
FIG. 10 is a diagram showing the result of a simulation of the trajectory of the charged particle in the present invention. - Modes for carrying out the present invention are hereinafter described with reference to the drawings.
FIGS. 1A and 1B are schematic configuration diagrams of a particle charger according to the present embodiment, whereFIG. 1A shows a vertical section of the particle charger, andFIG. 1B shows a section viewed along the arrows A-A inFIG. 1A .FIG. 2 is a perspective view of the filter in the same particle charger. It should be noted that the front-rear, up-down, and right-left directions mentioned in the following descriptions are defined so that the X, Y and Z directions inFIG. 1A correspond to the leftward, frontward and upward directions, respectively. - The particle charger according to the present embodiment, which is designed to be placed between the
sampler 100 and theclassifier 300 in a particle classifying and observing system as shown inFIG. 8 , includes a particle-chargingunit 20 and a gas-ion generating unit 10 (which corresponds to the gas ion supplier in the present invention) located above the former unit. - The particle-charging
unit 20 has a substantially rectangular parallelepiped chamber 21 (which corresponds to the housing in the present invention). On the left wall of thischamber 21, a first upward-side opening 22 (which corresponds to the particle introducer in the present invention) and a second upward-side opening 23 are vertically arranged, both of which are the openings for allowing an inflow of gas from the outside into thechamber 21. On the right wall of thechamber 21, a first downward-side opening 24 and a second downward-side opening 25 are vertically arranged, both of which are the openings for discharging gas from thechamber 21 to the outside. Thischamber 21 contains afirst plate electrode 26 arranged along the top face of thechamber 21, asecond plate electrode 27 arranged along the bottom face of thechamber 21, and afilter 28 located between the first andsecond plate electrodes filter 28 is composed of a plurality ofrod electrodes second plate electrodes filter 28 is composed of a large number ofelectrodes FIG. 2 . However, for simplicity, only sixelectrodes FIGS. 1A and 1B . Hereinafter, the space between thefirst plate electrode 26 and thefilter 28 is called the “first space 29”, while the space between thefilter 28 and thesecond plate electrode 27 is called the “second space 30”. - Provided outside the
chamber 21 of the particle-charging unit are aDC power source 31 for applying voltage V1 to thefirst plate electrode 26 and voltage V2 to thesecond plate electrode 27, as well as a firstAC power source 32 and a secondAC power source 33 for applying AC voltages to the electrodes forming thefilter 28. The first and secondAC power sources first plate electrode 26,second plate electrode 27 andDC power source 31 cooperating with each other function as the potential gradient creator in the present invention. The firstAC power source 32 supplies AC voltage V3 sin(ωt) to theelectrodes 28 a located at the odd-numbered positions as counted from the left end among the large number ofelectrodes filter 28. On the other hand, the secondAC power source 33 supplies AC voltage V4 sin(ωt+δ), which has a phase difference of δ from the AC voltage supplied by the firstAC power source 32, to theelectrodes 28 b located at the even-numbered positions as counted from the left end among the large number of electrodes. There is no specific limitation on the phase difference δ, although a value within a range of 90° to 270° is preferable. The amplitudes V3 and V4, frequency ω, as well as phase difference δ of the AC voltages supplied by the first and secondAC power sources controller 35. Thecontroller 35 also operates the aforementionedDC power source 31 and a discharge power source 14 (which will be described later), although the control lines for these devices are omitted from the figure for simplicity. - The gas-
ion generating unit 10 also has a substantiallyrectangular parallelepiped chamber 11, which contains a needle-shapeddischarge electrode 12 vertically extending downward from the top face. Located on the inner bottom of thesame chamber 11 is a plate-shapedground electrode 13 which forms a pair with thedischarge electrode 12. Outside thechamber 11, adischarge power source 14 for applying a voltage for inducing electric discharge to thedischarge electrode 12 is provided. Additionally, agas introduction port 15 for introducing a gas for gas-ion generation (“ionization gas”) into thechamber 11 is formed on the side wall of thechamber 11, while an opening for allowing an outflow of the ions generated within the chamber 11 (those ions are hereinafter called the “gas ions”) into thefirst space 29 is formed in the bottom wall of thechamber 11 Theground electrode 13, top wall of thechamber 21 of the particle-chargingunit 20, andfirst plate electrode 26 are also provided with through-holes formed at the position corresponding to the aforementioned opening. The opening and those through-holes form a gas-ion discharge port 16 through which the inner space of thechamber 21 of the particle-chargingunit 20 communicates with that of thechamber 11 of the gas-ion generating unit 10. - In the process of generating charged particles by the particle charger according to the present embodiment, an ionization gas (e.g. air) is initially introduced from the
gas introduction port 15 into thechamber 11 of the gas-ion generating unit 10, and a voltage is applied from thedischarge power source 14 to thedischarge electrode 12. As a result, electric discharge occurs in the space between thedischarge electrode 12 and theground electrode 13, whereby the ionization gas within thechamber 11 is ionized. The polarity of the thereby generated gas ions depends on the polarity of the voltage applied to thedischarge electrode 12. In the following description, it is assumed that the gas ions are positive ions. The gas ions generated in the gas-ion generating unit 10 flow through the gas-ion discharging port 16 into thefirst space 29 in the particle-chargingunit 20. - Meanwhile, the particles collected as the charging target by the sampler 100 (
FIG. 8 ) in the previous stage and carried by a carrier gas (e.g. air) are introduced from the first upward-side opening 22 into thefirst space 29. Simultaneously, a carrier gas supplied from a carrier gas supplier 34 (which does not contain the aforementioned particles) is introduced through the second upward-side opening 23 into thesecond space 30. As a result, a stream of carrier gas, directed from left to right, is formed within each of the first andsecond spaces FIG. 1A ). Thecarrier gas supplier 34, second upward-side opening 23 and second downward-side opening 25 correspond to the charged particle extractor in the present invention. - Since the
first space 29 contains gas ions at a high density, the particles to be charged introduced from the first upward-side opening 22 into thefirst space 29 come in contact with the gas ions and become positively charged by receiving electric charges from the gas ions. - Due to the voltage application by the
DC power source 31, the potential V1 of thefirst plate electrode 26 is higher than the potential V2 of thesecond plate electrode 27, i.e. V1>V2, whereby a potential gradient whose level decreases in the direction indicated by the thick white arrows inFIG. 1A is formed between the two electrodes. Since both the gas ions introduced into thefirst space 29 and the particles electrically charged within the first space 29 (which are hereinafter called the “charged particles”) are positively charged, they follow the potential gradient and move downward (i.e. toward the second space 30) within thechamber 21. - Meanwhile, the
filter 28 provided between the first andsecond spaces electrodes electrodes chamber 21 in the previously described manner alternately experience attractive and repulsive forces from theelectrodes electrodes - The charged panicles generated by the panicle charger in the present embodiment have sufficiently lower mobilities than the gas ions. Accordingly, by appropriately adjusting the values related to the conditions (amplitude, frequency and phase difference) of the voltages applied by the first and second
AC power sources filter 28 and reach thesecond space 30 while the gas ions are trapped by thefilter 28 and prevented from reaching thesecond space 30. In other words, as shown inFIG. 2 , the chargedparticles 42, whose mobility is relatively low oscillate in a stable manner and pass through the gaps between the neighboringelectrodes second space 30. On the other hand, thegas ions 41 whose mobility is relatively high, are attracted to and collide with theelectrode filter 28, failing to reach thesecond space 30. - The conditions of the voltages applied to the
filter 28 so as to allow the passage of only the charged particles in the previously described manner are, for example, previously investigated by experiments for each condition (kind, diameter, etc.) of the particles as the charging target and stored in astorage unit 36. When a target particle to be charged is specified by a user, thecontroller 35 refers to the information stored in thestorage unit 36, determines the conditions of the voltages corresponding to the target particle, and controls the first and secondAC power sources electrodes filter 28. - The charged particles which have reached the
second space 30 are carried rightwards within thesecond space 30 by the stream of ca gas directed from the second upward-side opening 23 to the second downward-side opening 25. Subsequently, the charged particles are extracted from the second downward-side opening 25 to the outside of thechamber 11 and sent to theparticle classifier 300 provided in the subsequent stage (FIG. 8 ). It should be noted that the amount of voltage applied from theDC power source 31, flow rate of the carrier gas supplied from thecarrier gas supplier 34 and other relevant parameters are previously adjusted by thecontroller 35 so that the charged particles which have passed through thefilter 28 and reached thesecond space 30 will be sent to the outside of thechamber 11 without colliding with thesecond plate electrode 27. - In this manner, in the particle charger according to the present embodiment, the charged particles generated by coming in contact with the gas ions are promptly extracted to the area where no gas ion is present (the second space 30), whereby the occurrence of the multi-charging is effectively suppressed and the ratio of singly-charged particles is increased. Therefore, in the process of extracting particles having a certain diameter by classification, the mixture of unwanted particles which have different diameters and yet have approximately the same mobility due to the multi-charging is suppressed. Therefore, for example, the accuracy of the particle diameter distribution can be improved, or a high level of collection efficiency can be achieved for particles having a specific particle diameter.
- The previously described example is concerned with the configuration in which the gas ions are positive ions and the particles are positively charged by corning into contact with those gas ions. It is also possible to use the opposite configuration in which the gas ions are negative ions and the particles are negatively charged by coming into contact with the gas ions. In this case, the potential V1 of the
first plate electrode 26 is set to be lower than the potential V2 of thesecond plate electrode 27. - In the previous example, the
electrodes filter 28 are arranged so that they extend in the right-left direction, i.e. in the orthogonal direction to the stream of the carrier gas. The arrangement is not limited to this form. For example, as shown inFIGS. 3A and 3B , the plurality ofelectrodes filter 51 may be arranged so that they extend in the front-rear direction, i.e. in the parallel direction to the stream of the carrier gas. - Other than the configuration in which straight electrodes are arranged parallel to each other as shown in
FIGS. 1A and 1B as well asFIGS. 3A and 3B , for example, the filter may be configured as shown inFIG. 4 in which thefilter 52 is composed a plurality ofelectrodes electrodes electrodes second plate electrodes 26 and 27 (in the up-down direction inFIG. 1A ). It is also possible to use a configuration as shown inFIG. 5 , in which thefilter 53 is composed of a plurality ofcircular electrodes FIG. 6 , in which thefilter 54 is composed of a plurality ofspiral electrodes electrodes - The cross-sectional shape of each electrode is also not specifically limited. Other than the circular shape as shown in
FIGS. 1A and 1B as well as andFIGS. 3A and 3B , it may have a polygonal shape, such as a triangle or quadrangle. - In the previous embodiment, the charged particles which have reached the
second space 30 are extracted to the outside of thechamber 21 by a stream of carrier gas. Alternatively, for example, the extraction of the charged particles may be achieved by an extracting electric field created within thesecond space 30. In this case, as shown inFIG. 7 , anextraction electrode 62 andopposite electrode 61 are arranged on the side wall of thechamber 21 of theparticle charger 20, facing each other across thesecond space 30, with a DC voltage applied between the two electrodes to create an extracting electric field having a potential gradient whose level decreases in the direction from theopposite electrode 61 toward the extraction electrode 62 (as indicated by the thick halftone arrows inFIG. 7 ). According to this configuration, the (positively) charged particles which have passed through thefilter 28 and reached thesecond space 30 in the previously described manner move in the direction from theopposite electrode 61 to theextraction electrode 62 and are eventually extracted from theopening 63 formed in theextraction electrode 62 to the outside of thechamber 11. In place of the plate-shaped electrode having the opening 63 as shown inFIG. 7 , a mesh-like electrode may be used as the extraction electrode, with the charged particles extracted through the openings of the mesh. In the case where the charged particles are negatively charged, an extracting electric field having the opposite potential gradient whose level increases from theopposite electrode 61 toward the extraction electrode is created. - Furthermore, the particle extractor in the present invention may also be configured to extract the charged particles by using both the stream of carrier gas and the extracting electric field. In this case, the
opposite electrode 61 inFIG. 7 is also be provided with an opening so as to introduce the carrier gas from this opening and thereby create a stream of carrier gas directed from the same opening toward theopening 63 of the extraction electrode. - The particle charger according to the present invention can be applied not only in a particle classifying and observing system as shown in
FIG. 8 ; for example, it can also be used as an ionizing unit in a mass spectrometer. - Hereinafter described is a simulation by numerical computation performed to confirm the effect of the particle charger according to the present invention. In this simulation, a system as shown in
FIGS. 1A and 1B was simulated under the following conditions: The voltage V1 applied to thefirst place electrode 26 was 1050 V. The voltage V2 applied to thesecond place electrode 27 was −1050 V. The AC voltage V3 sin(ωt) supplied from the firstAC power source 32 and the AC voltage V4 sin(ωt+δ) supplied from the secondAC power source 33 were set as follows: V3=V4=2000 V; ω=5, 25, 50, 250 and 500 Hz; and δ=π. Theelectrodes -
FIG. 9 shows the result of the simulation for the gas ions, andFIG. 10 shows the result of the simulation for the charged particles. The white circles in these drawings represent the cross section of the electrodes, while the lines in the same drawings represent the trajectories of the gas ions or charged particles. As shown inFIG. 9 , the gas ions travelling downward from each position in the space above the electrodes collide with one of the electrodes at any of the aforementioned frequencies of the AC voltage, failing to pass through the gap between the two electrodes. By comparison, in the case of the charged particles travelling downward from each position in the space above the electrodes, as shown inFIG. 10 , although a fraction of the particles collide with the electrodes, the largest portion of the particles pass through the gap between the two electrodes without colliding with the electrodes. The result also demonstrates that the ratio of the charged particles colliding with the electrodes decreases with an increase in the frequency of the AC voltage. -
- 10 . . . Gas-Ion Generating Unit
- 11 . . . Chamber
- 12 . . . Discharge Electrode
- 13 . . . Ground Electrode
- 14 . . . Discharge Power Source
- 15 . . . Gas Introduction Port
- 16 . . . Gas-Ion Discharge Port
- 20 . . . Particle Charging Unit
- 21 . . . Chamber
- 22 . . . First Upward-Side Opening
- 23 . . . Second Upward-Side Opening
- 24 . . . First Downward-Side Opening
- 25 . . . Second Downward-Side Opening
- 26 . . . First Plate Electrode
- 27 . . . Second Plate Electrode
- 28 . . . Filter
-
- 28 a . . . Electrode
- 28 b . . . Electrode
- 29 . . . First Space
- 30 . . . Second Space
- 31 . . . DC Power Source
- 32 . . . First AC Power Source
- 33 . . . Second AC Power Source
- 34 . . . Carrier Gas Supplier
- 35 . . . Controller
- 36 . . . Storage Unit
- 41 . . . Gas Ion
- 42 . . . Charged Particle
- 61 . . . Opposite Electrode
- 62 . . . Extraction Electrode
- 63 . . . Opening
Claims (12)
1. A particle charger, comprising:
a) a housing;
b) a filter composed of a plurality of electrodes extending in a virtual surface partitioning an inside of the housing into a first space and a second space;
c) a particle introducer for introducing a particle to be charged into the first space;
d) a gas ion supplier for supplying the first space with a gas ion;
e) a potential gradient creator for creating a potential gradient within the housing so as to make the gas ion and a charged particle resulting from a contact of the aforementioned particle with the gas ion move from the first space toward the second space;
f) an AC voltage supplier for applying an AC voltage to each of the electrodes forming the filter, where the voltages applied to any two electrodes neighboring each other among the plurality of electrodes have a phase difference;
g) a controller for controlling the AC voltage supplier so as to apply, to the plurality of electrodes, voltages which are previously determined so that, among the charged particle and the gas ion moving from the first space toward the second space, the charged particle is allowed to pass through a gap between the electrodes while the gas ion is trapped by one of the electrodes; and
h) a charged particle extractor for extracting the charged particle admitted to the second space to an outside of the housing.
2. The particle charger according to claim 1 , wherein the charged particle extractor produces a stream of carrier gas within the second space and carries the charged particle to the outside of the housing by the stream of carrier gas.
3. The particle charger according to claim 1 , wherein the charged particle extractor creates a potential gradient within the second space in a direction intersecting with the potential gradient and draws the charged particle to the outside of the housing by a motion of the charged particle along the former gradient.
4. The particle charger according to claim 1 , wherein the filter is composed of a plurality of rod electrodes arranged parallel to each other.
5. The particle charger according to claim 1 , wherein the filter is composed of a plurality of rod electrodes arranged in a form of a grid.
6. The particle charger according to claim 1 , wherein the filter is composed of a plurality of circular electrodes arranged in a concentric form.
7. The particle charger according to claim 2 , wherein the filter is composed of a plurality of rod electrodes arranged parallel to each other.
8. The particle charger according to claim 3 , wherein the filter is composed of a plurality of rod electrodes arranged parallel to each other.
9. The particle charger according to claim 2 , wherein the filter is composed of a plurality of rod electrodes arranged in a form of a grid.
10. The particle charger according to claim 3 , wherein the filter is composed of a plurality of rod electrodes arranged in a form of a grid.
11. The particle charger according to claim 2 , wherein the filter is composed of a plurality of circular electrodes arranged in a concentric form.
12. The particle charger according to claim 3 , wherein the filter is composed of a plurality of circular electrodes arranged in a concentric form.
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US20190285534A1 (en) * | 2018-03-19 | 2019-09-19 | Ngk Insulators, Ltd. | Particulate detector |
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CN107774451B (en) * | 2016-08-25 | 2023-12-15 | 宁波方太厨具有限公司 | Electrostatic purifying unit |
JP2018038988A (en) * | 2016-09-09 | 2018-03-15 | 株式会社島津製作所 | Particle concentrator |
JP2018077153A (en) * | 2016-11-10 | 2018-05-17 | 株式会社島津製作所 | Particle collector |
CN108918358A (en) * | 2018-07-17 | 2018-11-30 | 中煤科工集团重庆研究院有限公司 | A kind of particle size distributed detection system and method based on DMA |
KR102616653B1 (en) * | 2018-12-14 | 2023-12-21 | 삼성전자주식회사 | Carbon fiber charging device and home electric appliance having the same |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6444137B1 (en) * | 1990-07-31 | 2002-09-03 | Applied Materials, Inc. | Method for processing substrates using gaseous silicon scavenger |
Family Cites Families (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0722719B2 (en) * | 1985-09-02 | 1995-03-15 | 石川島播磨重工業株式会社 | Particle classification method and apparatus |
DE4025396A1 (en) * | 1990-08-10 | 1992-02-13 | Leybold Ag | DEVICE FOR PRODUCING A PLASMA |
US6003389A (en) * | 1996-09-05 | 1999-12-21 | California Institute Of Technology | Enhanced automated classified aerosol detector |
JP3787773B2 (en) * | 2002-05-10 | 2006-06-21 | 財団法人大阪産業振興機構 | Ionizer and system including the ionizer |
US7976673B2 (en) * | 2003-05-06 | 2011-07-12 | Lam Research Corporation | RF pulsing of a narrow gap capacitively coupled reactor |
JP4330466B2 (en) * | 2004-02-18 | 2009-09-16 | 浜松ホトニクス株式会社 | Monodispersed airborne particle classifier |
US7148472B2 (en) * | 2004-02-28 | 2006-12-12 | Ngx, Inc. | Aerosol mass spectrometer for operation in a high-duty mode and method of mass-spectrometry |
JP2007305498A (en) | 2006-05-15 | 2007-11-22 | Shimadzu Corp | Ion generating/emitting discharge electrode pair, ion generator using it, and ion generation device |
CN100523779C (en) * | 2006-06-12 | 2009-08-05 | 中国科学院合肥物质科学研究院 | System for investigating harmful nano-particle in air |
JP4779900B2 (en) * | 2006-09-15 | 2011-09-28 | 株式会社島津製作所 | Charging device |
JP4905040B2 (en) | 2006-10-06 | 2012-03-28 | 株式会社島津製作所 | Particle classifier |
US20090095714A1 (en) * | 2007-10-12 | 2009-04-16 | Tokyo Electron Limited | Method and system for low pressure plasma processing |
US8044350B2 (en) * | 2007-11-29 | 2011-10-25 | Washington University | Miniaturized ultrafine particle sizer and monitor |
JP2011003457A (en) * | 2009-06-19 | 2011-01-06 | Tokyo Electron Ltd | Charged particle separation apparatus and charged particle irradiation apparatus |
JP5236583B2 (en) * | 2009-06-19 | 2013-07-17 | 東京エレクトロン株式会社 | Charged particle sorting device and charged particle irradiation device |
US8309916B2 (en) * | 2010-08-18 | 2012-11-13 | Thermo Finnigan Llc | Ion transfer tube having single or multiple elongate bore segments and mass spectrometer system |
-
2014
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Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6444137B1 (en) * | 1990-07-31 | 2002-09-03 | Applied Materials, Inc. | Method for processing substrates using gaseous silicon scavenger |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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US20190285534A1 (en) * | 2018-03-19 | 2019-09-19 | Ngk Insulators, Ltd. | Particulate detector |
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US9875873B2 (en) | 2018-01-23 |
EP3195935A4 (en) | 2017-07-26 |
JPWO2016021063A1 (en) | 2017-04-27 |
CN106573253A (en) | 2017-04-19 |
EP3195935A1 (en) | 2017-07-26 |
WO2016021063A1 (en) | 2016-02-11 |
EP3195935B1 (en) | 2019-04-10 |
JP6210159B2 (en) | 2017-10-11 |
CN106573253B (en) | 2018-05-15 |
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